0.3 Acute Inflammation Flashcards
What are the mechanisms behind the four signs of inflammation?
Heat + Redness = increased blood flow
Swelling = vascular leakage / exudate
Pain = Increased sensitivity of pain receptors (hyperalgesia)
What are the differences between oedema, exudate, and pus?
Oedema = accumulation of fluid extravascularly in tissues
Exudate = oedema fluid with high protein content
Pus = Exudate containing viable and dead neutrophils, cel debris, microorganisms, proteins, lipids, DNA etc
What is the difference between purulent and suppuration?
Purulent = adjective form of pus
Suppuration = formation of pus
What are the 3 major components of acute inflammation in the order they occur?
- Dilation of small vessels = incread blood flow
- Increased microvascular permeability = plasma proteins and leukocytes leave circulation
- Emigration of leukocytes into extravascular tissue = accumulation in the focal area of injury
What are the 3 components of microcirculation?
- Arterioles
- Capillaries
- Post-capillary venules (PCV)
How does vasodilation cause hyperaemia in acute inflammation?
Normally, only some capillaries will transport blood
When inflamed, capillary beds open allowing ALL capillaries to transport blood in order to keep up with the increased blood flow from ateriolar and venular dilatation
Injury / infection causes the formation of vasoactive mediators and chemotactic factors. How do they lead to the formation of exudate in acute inflammation?
- Vasoactive mediators cause vasodilation and endothelial contraction = hyperaemia + increased hydrostatic pressure + increases vascular permeability in proteins
- Chemotactic factors activate neutrophils and increase adhesion molecules on endothelium = neutrophil margination and migration
- Hyperaemia + increased hydrostatic pressure + increased vascular permeability + neutrophil migration = fluid movement = exudate
Why is the exudation of fluid, plasma proteins, and neutrophils important?
Fluid = dilution of toxins + increase lymph flow
Plasma proteins = antibodes, complement system components + fibrin system components
Neutrophils = destruction of microorganisms
What changes in vascular flow occur during acute inflammation?
- Vasodilation = earliest manifestation
- Increased permeability of microvasculature
- Vascular congestion
What are the key characteristics of vasodilation?
Induced mostly by histamines in vascular smooth muscles
Affects arterioles first and subsequently capillary beds
Increased blood flow results in heat + redness
What is the difference between transudate and exudate?
Transudate = before increased microvasculature permeability, protein poor
Exudate = after increased microvasculature, permeability, outpouring of protein rich fluid
What are the key characteristics of vascular congestion?
Increased viscosity of blood = stasis (slow moving blood)
Results in loss of fluid and increased vessel diameter (engorgement)
Vascular leakage can occur for two reasons. What are they?
- Retraction of endothelial cells as a result of acute inflammation
- Endothelial injury (via burns, microbial toxins, or cholesterol)
What are the characteristics of endothelial cells caused vascular leakage?
- Induced by histamines + other mediators
- Results in opening of endothelial spaces to allow passage of neutrophils and exudate etc
- Occurs rapidly and is short lived (minutes)
What are the characteristics of endothelial injury caused vascular leakage?
- Endothelial cell necrosis + detachment from severe injury
- Rapid, but may be long-lived (hours to days)